transposes a matrix, ie. transform rows into columns

transpose_matrix.md

Kotlin

var transpose = { A: Array<IntArray> -> A[0].mapIndexed{ j, _ -> A.mapIndexed{ i, _ -> A[i][j] }.toIntArray() }.toTypedArray() }

Javascript

let transpose = A => A[0].map((_, j) => A.map((_, i) => A[i][j]));

Python3

transpose = lambda A: [[A[i][j] for i in range(len(A))] for j in range(len(A[0]))]